Final answer:
Chemicals enter the body through inhalation, ingestion, and skin absorption or penetration. These routes allow transport to internal organs where they can cause health effects. Breaks in the skin can also be a point of entry, as can eye contact with chemicals.
Step-by-step explanation:
The routes that chemicals enter the body are primarily through inhalation (breathing in through the lungs), ingestion (consuming through the mouth and entering the digestive tract), and skin absorption or penetration. These routes allow chemicals to be absorbed into the bloodstream where they could potentially reach internal "target" organs, such as the liver, kidneys, and nervous system.
Chemicals could also enter the body through parenteral routes, such as breaks in the skin. This includes wounds, insect bites, animal bites, or needle that bypass the natural barrier provided by intact skin and mucous membranes. Additionally, eye contact with chemicals can lead to absorption through the conjunctiva. It's important to note that inhalation and ingestion are separate processes; inhalation involves the respiratory system, while ingestion involves the digestive system.
Furthermore, it is possible for pharmaceutical substances to pass through the body without being fully metabolized and then be excreted in biologically active forms. This can result in them reaching the environment, particularly the aquatic environment, usually through urine.